High resistivity silicon-on-insulator wafer manufacturing method for reducing substrate loss

ABSTRACT

A multilayer composite structure and a method of preparing a multilayer composite structure are provided. The multilayer composite structure comprises a semiconductor handle substrate having a minimum bulk region resistivity of at least about 500 ohm-cm; a semiconductor nitride layer in contact with the semiconductor handle substrate, the semiconductor nitride layer selected from the group consisting of aluminum nitride, boron nitride, indium nitride, gallium nitride, aluminum gallium nitride, aluminum gallium indium nitride, aluminum gallium indium boron nitride, and combinations thereof; a dielectric layer in contact with the semiconductor nitride layer; and a semiconductor device layer in contact with the dielectric layer.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a divisional application of U.S. application Ser.No. 14/835,086, which was filed Aug. 25, 2015, which is herebyincorporated by reference as if set forth in its entirety. U.S.application Ser. No. 14/835,086 claims the benefit of provisionalapplication Ser. No. 62/045,602, filed Sep. 4, 2014, which is herebyincorporated by reference as if set forth in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of semiconductorwafer manufacture. More specifically, the present invention relates to amethod for producing a semiconductor-on-insulator (e.g.,silicon-on-insulator) structure, and more particularly to a method forproducing a charge trapping layer in the handle wafer of thesemiconductor-on-insulator structure.

BACKGROUND OF THE INVENTION

Semiconductor wafers are generally prepared from a single crystal ingot(e.g., a silicon ingot) which is trimmed and ground to have one or moreflats or notches for proper orientation of the wafer in subsequentprocedures. The ingot is then sliced into individual wafers. Whilereference will be made herein to semiconductor wafers constructed fromsilicon, other materials may be used to prepare semiconductor wafers,such as germanium, silicon carbide, silicon germanium, or galliumarsenide.

Semiconductor wafers (e.g., silicon wafers) may be utilized in thepreparation of composite layer structures. A composite layer structure(e.g., a semiconductor-on-insulator, and more specifically, asilicon-on-insulator (SOI) structure) generally comprises a handle waferor layer, a device layer, and an insulating (i.e., dielectric) film(typically an oxide layer) between the handle layer and the devicelayer. Generally, the device layer is between 0.01 and 20 micrometersthick. In general, composite layer structures, such assilicon-on-insulator (SOI), silicon-on-sapphire (SOS), andsilicon-on-quartz, are produced by placing two wafers in intimatecontact, followed by a thermal treatment to strengthen the bond.

After thermal anneal, the bonded structure undergoes further processingto remove a substantial portion of the donor wafer to achieve layertransfer. For example, wafer thinning techniques, e.g., etching orgrinding, may be used, often referred to as back etch SOI (i.e., BESOI),wherein a silicon wafer is bound to the handle wafer and then slowlyetched away until only a thin layer of silicon on the handle waferremains. See, e.g., U.S. Pat. No. 5,189,500, the disclosure of which isincorporated herein by reference as if set forth in its entirety. Thismethod is time-consuming and costly, wastes one of the substrates andgenerally does not have suitable thickness uniformity for layers thinnerthan a few microns.

Another common method of achieving layer transfer utilizes a hydrogenimplant followed by thermally induced layer splitting. Particles (e.g.,hydrogen atoms or a combination of hydrogen and helium atoms) areimplanted at a specified depth beneath the front surface of the donorwafer. The implanted particles form a cleave plane in the donor wafer atthe specified depth at which they were implanted. The surface of thedonor wafer is cleaned to remove organic compounds deposited on thewafer during the implantation process.

The front surface of the donor wafer is then bonded to a handle wafer toform a bonded wafer through a hydrophilic bonding process. Prior tobonding, the donor wafer and/or handle wafer are activated by exposingthe surfaces of the wafers to plasma containing, for example, oxygen ornitrogen. Exposure to the plasma modifies the structure of the surfacesin a process often referred to as surface activation, which activationprocess renders the surfaces of one or both of the donor water andhandle wafer hydrophilic. The wafers are then pressed together, and abond is formed there between. This bond is relatively weak, and must bestrengthened before further processing can occur.

In some processes, the hydrophilic bond between the donor wafer andhandle wafer (i.e., a bonded wafer) is strengthened by heating orannealing the bonded wafer pair. In some processes, wafer bonding mayoccur at low temperatures, such as between approximately 300° C. and500° C. In some processes, wafer bonding may occur at high temperatures,such as between approximately 800° C. and 1100° C. The elevatedtemperatures cause the formation of covalent bonds between the adjoiningsurfaces of the donor wafer and the handle wafer, thus solidifying thebond between the donor wafer and the handle wafer. Concurrently with theheating or annealing of the bonded wafer, the particles earlierimplanted in the donor wafer weaken the cleave plane.

A portion of the donor wafer is then separated (i.e., cleaved) along thecleave plane from the bonded wafer to form the SOI wafer. Cleaving maybe carried out by placing the bonded wafer in a fixture in whichmechanical force is applied perpendicular to the opposing sides of thebonded wafer in order to pull a portion of the donor wafer apart fromthe bonded wafer. According to some methods, suction cups are utilizedto apply the mechanical force. The separation of the portion of thedonor wafer is initiated by applying a mechanical wedge at the edge ofthe bonded wafer at the cleave plane in order to initiate propagation ofa crack along the cleave plane. The mechanical force applied by thesuction cups then pulls the portion of the donor wafer from the bondedwafer, thus forming an SOI wafer.

According to other methods, the bonded pair may instead be subjected toan elevated temperature over a period of time to separate the portion ofthe donor wafer from the bonded wafer. Exposure to the elevatedtemperature causes initiation and propagation of a crack along thecleave plane, thus separating a portion of the donor wafer. This methodallows for better uniformity of the transferred layer and allows recycleof the donor wafer, but typically requires heating the implanted andbonded pair to temperatures approaching 500° C.

The use of high resistivity semiconductor-on-insulator (e.g.,silicon-on-insulator) wafers for RF related devices such as antennaswitches offers benefits over traditional substrates in terms of costand integration. To reduce parasitic power loss and minimize harmonicdistortion inherent when using conductive substrates for high frequencyapplications it is necessary, but not sufficient, to use substratewafers with a high resistivity. Accordingly, the resistivity of thehandle wafer for an RF device is generally greater than about 500Ohm-cm. With reference now to FIG. 1, a silicon on insulator structure 2comprising a very high resistivity silicon wafer 4, a buried oxide (BOX)layer 6, and a silicon device layer 10. Such a substrate is prone toformation of high conductivity charge inversion or accumulation layers12 at the BOX/handle interface causing generation of free carriers(electrons or holes), which reduce the effective resistivity of thesubstrate and give rise to parasitic power losses and devicenonlinearity when the devices are operated at RF frequencies. Theseinversion/accumulation layers can be due to BOX fixed charge, oxidetrapped charge, interface trapped charge, and even DC bias applied tothe devices themselves.

A method is required therefore to trap the charge in any inducedinversion or accumulation layers so that the high resistivity of thesubstrate is maintained even in the very near surface region. It isknown that charge trapping layers (CTL) between the high resistivityhandle substrates and the buried oxide (BOX) may improve the performanceof RF devices fabricated using SOI wafers. A number of methods have beensuggested to form these high interface trap layers. For example, withreference now to FIG. 2, one of the method of creating asemiconductor-on-insulator 20 (e.g., a silicon-on-insulator, or SOI)with a CTL for RF device applications is based on depositing an undopedpolycrystalline silicon film 28 on a silicon substrate having highresistivity 22 and then forming a stack of oxide 24 and top siliconlayer 26 on it. A polycrystalline silicon layer 28 acts as a highdefectivity layer between the silicon substrate 22 and the buried oxidelayer 24. See FIG. 2, which depicts a polycrystalline silicon film foruse as a charge trapping layer 28 between a high resistivity substrate22 and the buried oxide layer 24 in a silicon-on-insulator structure 20.An alternative method is the implantation of heavy ions to create a nearsurface damage layer. Devices, such as radiofrequency devices, are builtin the top silicon layer 26.

It has been shown in academic studies that the polycrystalline siliconlayer in between of the oxide and substrate improves the deviceisolation, decreases transmission line losses and reduces harmonicdistortions. See, for example: H. S. Gamble, et al. “Low-loss CPW lineson surface stabilized high resistivity silicon,” Microwave Guided WaveLett., 9(10), pp. 395-397, 1999; D. Lederer, R. Lobet and J.-P. Raskin,“Enhanced high resistivity SOI wafers for RF applications,” IEEE Intl.SOI Conf, pp. 46-47, 2004; D. Lederer and J.-P. Raskin, “New substratepassivation method dedicated to high resistivity SOI wafer fabricationwith increased substrate resistivity,” IEEE Electron Device Letters,vol. 26, no. 11, pp. 805-807, 2005; D. Lederer, B. Aspar, C. Laghaé andJ.-P. Raskin, “Performance of RF passive structures and SOI MOSFETstransferred on a passivated HR SOI substrate,” IEEE International SOIConference, pp. 29-30, 2006; and Daniel C. Kerr et al. “Identificationof RF harmonic distortion on Si substrates and its reduction using atrap-rich layer”, Silicon Monolithic Integrated Circuits in RF Systems,2008. SiRF 2008 (IEEE Topical Meeting), pp. 151-154, 2008.

SUMMARY OF THE INVENTION

Among the provisions of the present invention may be noted a multilayerstructure comprising: a semiconductor handle substrate comprising twomajor, generally parallel surfaces, one of which is a front surface ofthe semiconductor handle substrate and the other of which is a backsurface of the semiconductor handle substrate, a circumferential edgejoining the front and back surfaces of the semiconductor handlesubstrate, and a bulk region between the front and back surfaces of thesemiconductor handle substrate, wherein the semiconductor handlesubstrate has a minimum bulk region resistivity of at least about 500ohm-cm; a semiconductor nitride layer in contact with the front surfaceof the semiconductor handle substrate, the semiconductor nitride layerselected from the group consisting of aluminum nitride, boron nitride,indium nitride, gallium nitride, aluminum gallium nitride, aluminumgallium indium nitride, aluminum gallium indium boron nitride, andcombinations thereof; a dielectric layer in contact with thesemiconductor nitride layer; and a semiconductor device layer in contactwith the dielectric layer.

The present invention is further directed to a method of forming amultilayer structure, the method comprising: forming a semiconductornitride layer on a front surface of a semiconductor handle substrate,wherein the semiconductor nitride layer is selected from the groupconsisting of aluminum nitride, boron nitride, indium nitride, galliumnitride, aluminum gallium nitride, aluminum gallium indium nitride,aluminum gallium indium boron nitride, and combinations thereof andwherein the semiconductor handle substrate comprises two major,generally parallel surfaces, one of which is the front surface of thesemiconductor handle substrate and the other of which is a back surfaceof the semiconductor handle substrate, a circumferential edge joiningthe front and back surfaces of the semiconductor handle substrate, and abulk region between the front and back surfaces of the semiconductorhandle substrate, wherein the semiconductor handle substrate has aminimum bulk region resistivity of at least about 500 ohm-cm; andbonding a front surface of a semiconductor donor substrate to thesemiconductor nitride layer to thereby form a bonded structure, whereinthe semiconductor donor substrate comprises two major, generallyparallel surfaces, one of which is the front surface of thesemiconductor donor substrate and the other of which is a back surfaceof the semiconductor donor substrate, a circumferential edge joining thefront and back surfaces of the semiconductor donor substrate, and acentral plane between the front and back surfaces of the semiconductordonor substrate, and further wherein the front surface of thesemiconductor donor substrate comprises a dielectric layer.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a depiction of a silicon-on-insulator wafer comprising a highresistivity substrate and a buried oxide layer.

FIG. 2 is a depiction of a silicon-on-insulator wafer according to theprior art, the SOI wafer comprising a polysilicon charge trapping layerbetween a high resistivity substrate and a buried oxide layer.

FIG. 3 is a depiction of a high resistivity silicon-on-insulatorcomposite structure with an embedded wide bandgap layer.

FIG. 4 is an XTEM image of aluminum nitride grown on a silicon substrateby metalorganic chemical vapor deposition (MOCVD).

DETAILED DESCRIPTION OF THE EMBODIMENT(S) OF THE INVENTION

According to the present invention, a method is provided for preparing asemiconductor-on-insulator composite structure comprising a wide bandgaplayer comprising a semiconductor nitride, e.g., a Group IIIA nitride, ona semiconductor handle substrate, e.g., a single crystal semiconductorhandle wafer, such as a single crystal silicon handle wafer. The presentinvention is further directed to a semiconductor handle wafer comprisinga wide bandgap layer on a surface thereof. The single crystalsemiconductor handle wafer comprising the wide bandgap layer is usefulin the production of a semiconductor-on-insulator (e.g.,silicon-on-insulator) structure. The present invention is thus furtherdirected to a semiconductor-on-insulator composite structure comprisinga semiconductor handle wafer comprising a wide bandgap layer comprisinga semiconductor nitride, e.g., a Group IIIA nitride. The wide bandgaplayer comprising the Group IIIA nitride is located at the interface ofthe semiconductor handle wafer and the dielectric layer, e.g., a buriedoxide, or BOX layer, which itself interfaces with a semiconductor devicelayer.

According to the present invention, the wide bandgap layer is formed ona surface of a semiconductor handle substrate, e.g., a single crystalsemiconductor handle wafer, such as a single crystal silicon handlewafer, at the region near the oxide interface. The incorporation of awide bandgap layer at the region near the high resistivity semiconductorwafer-buried oxide interface is advantageous since defects in wide bandgap materials tend to have deep energy levels. The carriers that aretrapped deep in the bandgap require more energy to be released, whichenhances the effectiveness of a wide bandgap layer as a charge trappinglayer. Wide bandgap layer materials include Group IIIA (boron group, oricosagens) nitrides. Such materials may be selected from among aluminumnitride, boron nitride, indium nitride, gallium nitride, aluminumgallium nitride, aluminum gallium indium nitride, aluminum galliumindium boron nitride, and combinations thereof.

The substrates for use in the present invention include a semiconductorhandle substrate, e.g., a single crystal semiconductor handle wafer, anda semiconductor donor substrate, e.g., a single crystal semiconductordonor wafer. FIG. 3 is a depiction of an exemplary, non-limiting highresistivity silicon-on-insulator composite structure with an embeddedwide bandgap layer. The semiconductor device layer 106 in asemiconductor-on-insulator composite structure 100 is derived from thesingle crystal semiconductor donor wafer. The semiconductor device layer106 may be transferred onto the semiconductor handle substrate 102 bywafer thinning techniques such as etching a semiconductor donorsubstrate or by cleaving a semiconductor donor substrate comprising adamage plane. In general, the single crystal semiconductor handle waferand single crystal semiconductor donor wafer comprise two major,generally parallel surfaces. One of the parallel surfaces is a frontsurface of the substrate, and the other parallel surface is a backsurface of the substrate. The substrates comprise a circumferential edgejoining the front and back surfaces, and a central plane between thefront and back surfaces. The substrates additionally comprise animaginary central axis perpendicular to the central plane and a radiallength that extends from the central axis to the circumferential edge.In addition, because semiconductor substrates, e.g., silicon wafers,typically have some total thickness variation (TTV), warp, and bow, themidpoint between every point on the front surface and every point on theback surface may not precisely fall within a plane. As a practicalmatter, however, the TITV, warp, and bow are typically so slight that toa close approximation the midpoints can be said to fall within animaginary central plane which is approximately equidistant between thefront and back surfaces.

Prior to any operation as described herein, the front surface and theback surface of the substrate may be substantially identical. A surfaceis referred to as a “front surface” or a “back surface” merely forconvenience and generally to distinguish the surface upon which theoperations of method of the present invention are performed. In thecontext of the present invention, a “front surface” of a single crystalsemiconductor handle substrate 102, e.g., a single crystal siliconhandle wafer, refers to the major surface of the substrate that becomesan interior surface of the bonded structure. It is upon this frontsurface that the wide bandgap layer 108 is formed. Accordingly, a “backsurface” of a single crystal semiconductor handle substrate, e.g., ahandle wafer, refers to the major surface that becomes an exteriorsurface of the bonded structure. Similarly, a “front surface” of asingle crystal semiconductor donor substrate, e.g., a single crystalsilicon donor wafer, refers to the major surface of the single crystalsemiconductor donor substrate that becomes an interior surface of thebonded structure, and a “back surface” of a single crystal semiconductordonor substrate, e.g., a single crystal silicon donor wafer, refers tothe major surface that becomes an exterior surface of the bondedstructure. Upon completion of conventional bonding and wafer thinningsteps, the single crystal semiconductor donor substrate forms thesemiconductor device layer 106 of the semiconductor-on-insulator (e.g.,silicon-on-insulator) composite structure.

The single crystal semiconductor handle substrate and the single crystalsemiconductor donor substrate may be single crystal semiconductorwafers. In preferred embodiments, the semiconductor wafers comprise amaterial selected from the group consisting of silicon, silicon carbide,silicon germanium, gallium arsenide, gallium nitride, indium phosphide,indium gallium arsenide, germanium, and combinations thereof. The singlecrystal semiconductor wafers, e.g., the single crystal silicon handlewafer and single crystal silicon donor wafer, of the present inventiontypically have a nominal diameter of at least about 150 mm, at leastabout 200 mm, at least about 300 mm, at least about 450 mm, or more.Wafer thicknesses may vary from about 250 micrometers to about 1500micrometers, suitably within the range of about 500 micrometers to about1000 micrometers.

In particularly preferred embodiments, the single crystal semiconductorwafers comprise single crystal silicon wafers which have been slicedfrom a single crystal ingot grown in accordance with conventionalCzochralski crystal growing methods or float zone growing methods. Suchmethods, as well as standard silicon slicing, lapping, etching, andpolishing techniques are disclosed, for example, in F. Shimura,Semiconductor Silicon Crystal Technology, Academic Press, 1989, andSilicon Chemical Etching, (J. Grabmaier ed.) Springer-Verlag, N.Y., 1982(incorporated herein by reference). Preferably, the wafers are polishedand cleaned by standard methods known to those skilled in the art. See,for example, W. C. O'Mara et al., Handbook of Semiconductor SiliconTechnology, Noyes Publications. If desired, the wafers can be cleaned,for example, in a standard SC1/SC2 solution. In some embodiments, thesingle crystal silicon wafers of the present invention are singlecrystal silicon wafers which have been sliced from a single crystalingot grown in accordance with conventional Czochralski (“Cz”) crystalgrowing methods, typically having a nominal diameter of at least about150 mm, at least about 200 mm, at least about 300 mm, at least about 450mm, or more. Preferably, both the single crystal silicon handle waferand the single crystal silicon donor wafer have mirror-polished frontsurface finishes that are free from surface defects, such as scratches,large particles, etc. Wafer thickness may vary from about 250micrometers to about 1500 micrometers, suitably within the range ofabout 500 micrometers to about 1000 micrometers. In some specificembodiments, the wafer thickness may be about 725 micrometers.

In some embodiments, the single crystal semiconductor wafers, i.e.,handle wafer and donor wafer, comprise interstitial oxygen inconcentrations that are generally achieved by the Czochralski-growthmethod. In some embodiments, the semiconductor wafers comprise oxygen ina concentration between about 4 PPMA and about 18 PPMA. In someembodiments, the semiconductor wafers comprise oxygen in a concentrationbetween about 10 PPMA and about 35 PPMA. Interstitial oxygen may bemeasured according to SEMI MF 1188-1105.

In some embodiments, the semiconductor handle substrate 102, e.g., asingle crystal semiconductor handle substrate, such as a single crystalsilicon handle wafer, has a relatively high minimum bulk resistivity.High resistivity wafers are generally sliced from single crystal ingotsgrown by the Czochralski method or float zone method. Cz-grown siliconwafers may be subjected to a thermal anneal at a temperature rangingfrom about 600° C. to about 1000° C. in order to annihilate thermaldonors caused by oxygen that are incorporated during crystal growth. Insome embodiments, the single crystal semiconductor handle wafer has aminimum bulk resistivity of at least 100 Ohm-cm, such as between about100 Ohm-cm and about 100,000 Ohm-cm, or between about 500 Ohm-cm andabout 100,000 Ohm-cm, or between about 1000 Ohm-cm and about 100,000Ohm-cm, or between about 500 Ohm-cm and about 10,000 Ohm-cm, or betweenabout 750 Ohm-cm and about 10,000 Ohm-cm, between about 1000 Ohm-cm andabout 10,000 Ohm-cm, between about 2000 Ohm-cm and about 10,000 Ohm-cm,between about 3000 Ohm-cm and about 10,000 Ohm-cm, or between about 3000Ohm-cm and about 5,000 Ohm-cm. Methods for preparing high resistivitywafers are known in the art, and such high resistivity wafers may beobtained from commercial suppliers, such as SunEdison Semiconductor Ltd.(St. Peters, Mo.; formerly MEMC Electronic Materials, Inc.).

In some embodiments, the front surface of the semiconductor handlesubstrate 102 is cleaned to remove all oxide prior to formation of thewide bandgap layer such that the front surface of the wafer lacks even anative oxide layer. The native oxide may be removed by standard etchingtechniques. In some embodiments, the semiconductor wafer may besubjected to a vapor phase HCl etch process in a horizontal flow singlewafer epitaxial reactor using H₂ as a carrier gas.

In some embodiments, a wide bandgap layer 108 is deposited on the frontsurface of the semiconductor handle substrate 102, e.g., a wafer. Widebandgap layer materials include semiconductor nitrides, e.g., Group IIIA(boron group, or icosagens) nitrides. Group IIIA elements comprisealuminum, boron, indium, and gallium. Accordingly, Group IIIA nitridesmay be selected from among aluminum nitride, boron nitride, indiumnitride, gallium nitride, aluminum gallium nitride, aluminum galliumindium nitride, aluminum gallium indium boron nitride, and combinationsthereof. The Group IIIA material may be crystalline or amorphous. Thelayer of wide bandgap material deposited on the front surface of thehandle wafer may comprise multiple layers of Group IIIA nitrides, andeach layer may comprise the same material, or different materials. Thewide bandgap materials of the present invention may be deposited bymetalorganic chemical vapor deposition (MOCVD), physical vapordeposition (PVD), chemical vapor deposition (CVD), or molecular beamepitaxy (MBE). In some preferred embodiments, the wide bandgap materialsof the present invention may be deposited by metalorganic chemical vapordeposition (MOCVD). In some embodiments, MOCVD may be carried out in acommercially available instrument suitable for MOCVD, such as the VeecoTurbodisc K465i or the Aixtron G5. MOCVD is particularly preferred sinceit enables higher growth temperature, better uniformity, and lowersurface roughness. In MOCVD, gaseous precursors are injected into areactor, and the reaction between the precursors deposit a layer ofatoms onto a semiconductor wafer. Surface reaction of organic compoundsor metalorganics and nitrogen-containing precursors create conditionsfor crystalline growth. Aluminum precursors suitable for MOCVD includetrimethylaluminum and triethylaluminum. Gallium precursors for MOCVDinclude trimethylgallium and triethylgallium. Indium precursors suitablefor MOCVD include trimethylindium, triethylindium,di-isopropylmethylindium, and ethyldimethylindium. Nitrogen precursorssuitable for MOCVD include Ammonium, phenyl hydrazine, dimethylhydrazine, tertiary butyl amine, and ammonia. Boron precursors includediborane, boronchloride, 1,3,5-tri(N-methyl)borazine. The molar ratio ofGroup V precursor (e.g., ammonia) to Group III precursor (e.g.,trimethyl gallium) may be between 1 to 10000, preferably between 100 to1000.

In some embodiments, the crystalline or amorphous semiconductor nitridelayer comprises aluminum nitride. In some embodiments, the crystallineor amorphous semiconductor nitride layer comprises boron nitride.Aluminum nitride and boron nitride are advantageous since thesematerials exhibit high thermal stability. In some embodiments, thecrystalline semiconductor nitride layer comprises indium nitride. Insome embodiments, the crystalline semiconductor nitride layer comprisesgallium nitride. In some embodiments, the crystalline semiconductor maycontain the mixture of Ga, In, Al nitride, like GaInAlN, GaInAlBN. Insome embodiments, the crystalline semiconductor may contain mixed layersof AlN, GaN, InN, or BN. The employment of different layers providesprocess integration advantages, like film stress management anddiffusion barrier. An example is GaN/AlN/Si, where, AlN is a seed layerfor GaN growth and it also blocks Ga diffusion into Si substrates.

A MOCVD reactor comprises a chamber comprising reactor walls, liner, asusceptor, gas injection units, and temperature control units. The partsof the reactor are made of materials resistant to and non-reactive withthe precursor materials. To prevent overheating, cooling water may beflowing through the channels within the reactor walls. A substrate sitson a susceptor which is at a controlled temperature. The susceptor ismade from a material resistant to the metalorganic compounds used, suchas SiC or graphite. For growing nitrides and related materials, aspecial coating on the graphite susceptor may be used to preventcorrosion by ammonia (NH₃) gas. Reactive gas is introduced by an inletthat controls the ratio of precursor reactants. A wide bandgap materialcomprising a Group IIIA nitride may be deposited to a thickness betweenabout 1 nanometer and about 2000 nanometers, or between about 5nanometers and about 2000 nanometers, or between about 5 nanometers andabout 1000 nanometers, or between about 5 nanometers and about 500nanometers, or between about 5 nanometers and about 200 nanometers, suchas between about 10 nanometers and about 100 nanometers by MOCVD on ahigh resistivity semiconductor handle substrate. The growth temperaturemay be between about 600° C. and about 1200° C., such as between about800° C. and about 1200° C., preferably between about 1000° C. and about1150° C. The Group IIIA nitride may be formed under reduced pressure,such as between about 10⁻¹¹ Torr (about 1×10⁻⁹ Pa) to about 760 Torr(about 101 kPa), or between about 1 Torr (about 0.13 kPa) and about 400Torr (about 53.3 kPa), preferably between about 10 Torr (about 1.33 kPa)and about 80 Torr (about 10.67 kPa).

After deposition of the wide bandgap layer 108, optionally a dielectriclayer may be formed on top of the wide bandgap layer. In someembodiments, the dielectric layer comprises an oxide film or a nitridefilm. Suitable dielectric layers may comprise a material selected fromamong silicon dioxide, silicon nitride, hafnium oxide, titanium oxide,zirconium oxide, lanthanum oxide, barium oxide, and combinationsthereof. In some embodiments, the dielectric layer comprises an oxidefilm. Such an oxide film may serve as a bonding surface with anoptionally oxidized semiconductor device substrate and thus may beincorporated into the dielectric layer 104 in the finalsemiconductor-on-insulator composite structure 100. In some embodiments,the dielectric layer comprises silicon dioxide, which may be depositedby means known in the art, such as CVD oxide deposition. In someembodiments, the silicon dioxide layer thickness can be between about100 nanometers to about 5 micrometers, such as between about 500nanometers and about 2 micrometers, or between about 700 nanometers andabout 1 micrometer.

After oxide deposition, wafer cleaning is optional. If desired, thewafers can be cleaned, for example, in a standard SC1/SC2 solution.Additionally, the wafers may be subjected to chemical mechanicalpolishing (CMP) to reduce the surface roughness, preferably to the levelof RMS_(2×2 um2) is less than about 50 angstroms, even more preferablyless than about 5 angstroms, wherein root mean squared

${R_{q} = \sqrt{\frac{1}{n}{\sum\limits_{i = 1}^{n}y_{i}^{2}}}},$the roughness profile contains ordered, equally spaced points along thetrace, and y_(i) is the vertical distance from the mean line to the datapoint.

The semiconductor handle substrate 102, e.g. a single crystalsemiconductor handle wafer such as a single crystal silicon handlewafer, prepared according to the method described herein to comprise awide bandgap layer 108 and, optionally, an oxide film, is next bonded asemiconductor donor substrate, e.g., a single crystal semiconductordonor wafer, which is prepared according to conventional layer transfermethods. That is, the single crystal semiconductor donor substrate,e.g., a single crystal semiconductor wafer, may be subjected to standardprocess steps including oxidation, implant, and post implant cleaning.Accordingly, a semiconductor donor substrate, such as a single crystalsemiconductor wafer of a material that is conventionally used inpreparation of multilayer semiconductor structures, e.g., a singlecrystal silicon donor wafer, that has been etched and polished andoptionally oxidized, is subjected to ion implantation to form a damagelayer in the donor substrate. In some embodiments, the semiconductordonor substrate comprises a dielectric layer. Suitable dielectric layersmay comprise a material selected from among silicon dioxide, siliconnitride, hafnium oxide, titanium oxide, zirconium oxide, lanthanumoxide, barium oxide, and a combination thereof. In some embodiments, thedielectric layer comprises an oxide layer having a thickness from about10 nanometers to about 500 nanometers, such as between about 100nanometers and about 400 nanometers.

Ion implantation may be carried out in a commercially availableinstrument, such as an Applied Materials Quantum II. Implanted ionsinclude He, H, H₂, or combinations thereof. Ion implantation is carriedout as a density and duration sufficient to form a damage layer in thesemiconductor donor substrate. Implant density may range from about 10¹²ions/cm² to about 10¹⁶ ions/cm². Implant energies may range from about 1keV to about 3,000 keV. In some embodiments it may be desirable tosubject the single crystal semiconductor donor wafers, e.g., singlecrystal silicon donor wafers, to a clean after the implant. In somepreferred embodiments, the clean could include a Piranha clean followedby a DI water rinse and SC1/SC2 cleans.

In some embodiments, the ion-implanted and optionally cleaned singlecrystal semiconductor donor substrate is subjected to oxygen plasmaand/or nitrogen plasma surface activation. In some embodiments, theoxygen plasma surface activation tool is a commercially available tool,such as those available from EV Group, such as EVG® 810LT Low TempPlasma Activation System. The ion-implanted and optionally cleanedsingle crystal semiconductor donor wafer is loaded into the chamber. Thechamber is evacuated and backfilled with O₂ to a pressure less thanatmospheric to thereby create the plasma. The single crystalsemiconductor donor wafer is exposed to this plasma for the desiredtime, which may range from about 1 second to about 120 seconds. Oxygenplasma surface oxidation is performed in order to render the frontsurface of the single crystal semiconductor donor substrate hydrophilicand amenable to bonding to a single crystal semiconductor handlesubstrate prepared according to the method described above.

The hydrophilic front surface layer of the single crystal semiconductordonor substrate and the front surface of the single crystalsemiconductor handle substrate, which is optionally oxidized, are nextbrought into intimate contact to thereby form a bonded structure. Sincethe mechanical bond is relatively weak, the bonded structure is furtherannealed to solidify the bond between the donor wafer and the handlewafer. In some embodiments of the present invention, the bondedstructure is annealed at a temperature sufficient to form a thermallyactivated cleave plane in the single crystal semiconductor donorsubstrate. An example of a suitable tool might be a simple Box furnace,such as a Blue M model. In some preferred embodiments, the bondedstructure is annealed at a temperature of from about 200° C. to about350° C., from about 225° C. to about 325° C., preferably about 300° C.Thermal annealing may occur for a duration of from about 0.5 hours toabout 10 hour, preferably a duration of about 2 hours. Thermal annealingwithin these temperatures ranges is sufficient to form a thermallyactivated cleave plane. After the thermal anneal to activate the cleaveplane, the bonded structure may be cleaved.

After the thermal anneal, the bond between the single crystalsemiconductor donor substrate and the single crystal semiconductorhandle substrate is strong enough to initiate layer transfer viacleaving the bonded structure at the cleave plane. Cleaving may occuraccording to techniques known in the art. In some embodiments, thebonded structure may be placed in a conventional cleave station affixedto stationary suction cups on one side and affixed by additional suctioncups on a hinged arm on the other side. A crack is initiated near thesuction cup attachment and the movable arm pivots about the hingecleaving the wafer apart. Cleaving removes a portion of thesemiconductor donor wafer, thereby leaving a semiconductor device layer,preferably a silicon device layer, on the semiconductor-on-insulatorcomposite structure.

After cleaving, the cleaved structure is subjected to a high temperatureanneal in order to further strengthen the bond between the transferreddevice layer and the single crystal semiconductor handle substrate. Anexample of a suitable tool might be a vertical furnace, such as an ASMA400. In some preferred embodiments, the bonded structure is annealed ata temperature of from about 1000° C. to about 1200° C., preferably atabout 1000° C. Thermal annealing may occur for a duration of from about0.5 hours to about 8 hours, preferably a duration of about 4 hours.Thermal annealing within these temperatures ranges is sufficient tostrengthen the bond between the transferred device layer and the singlecrystal semiconductor handle substrate.

After the cleave and high temperature anneal, the bonded structure maybe subjected to a cleaning process designed to remove thin thermal oxideand clean particulates from the surface. In some embodiments, the singlecrystal semiconductor device layer may be brought to the desiredthickness and smoothness by subjecting to a vapor phase HCl etch processin a horizontal flow single wafer epitaxial reactor using H₂ as acarrier gas. In some embodiments, an epitaxial layer may be deposited onthe transferred device layer. The finished SOI wafer comprises thesemiconductor handle substrate, the Group IIIA nitride layer, thedielectric layer (e.g., buried oxide layer), and the semiconductordevice layer, may then be subjected to end of line metrology inspectionsand cleaned a final time using typical SC1-SC2 process.

According to the present invention, and with reference to FIG. 3, asemiconductor-on-insulator composite structure 100 is obtained with thewide bandgap layer 108 forming an interface with a high resistivitysubstrate 102 and with a dielectric layer 104. The dielectric layer 104is in interface with a semiconductor device layer 106. The dielectriclayer 104 may comprise a buried oxide, or BOX. The wide bandgap layer108 comprises a semiconductor nitride, e.g., a Group IIIA nitride, ininterface with the dielectric layer 104 in a semiconductor-on-insulatorcomposite structure 100 can be effective for preserving charge trappingefficiency of the films during high temperature treatments.

Having described the invention in detail, it will be apparent thatmodifications and variations are possible without departing from thescope of the invention defined in the appended claims.

EXAMPLES

The following non-limiting examples are provided to further illustratethe present invention.

Example 1. Silicon-on-Insulator Structure Comprising Aluminum NitrideCharge Trapping Layer

A silicon-on-insulator structure 100 of the invention is depicted inFIG. 3. A thin crystalline charge trapping layer 108 comprising aluminumnitride (100 nm) is grown by MOCVD on top of high resistivity siliconhandle substrate 102 with the growth temperature of 1100° C. Aluminumnitride is formed under reduced pressure of 40 Torr. This substrate wasused in the production of a silicon-on-insulator structure 100 furthercomprising an insulator layer of silicon dioxide 104 and a silicondevice layer 106. FIG. 4 depicts the bright field cross-section TEMimage of the 100 nm aluminum nitride layer grown on the siliconsubstrate by MOCVD. The dislocation network creates a high density ofpotential charge traps. About 7600 angstroms SiO₂, as part of theinsulator layer 104, is then deposited on top of AlN layer 108. Aconventional donor wafer with about 2400 angstroms SiO₂ can then beimplanted and bonded to the handle substrate by conventional techniques.The SOI structure is then heat treated, cleaved, and gone throughmultiple thermal processes to reach the end of line with standardprocess flow.

When introducing elements of the present invention or the preferredembodiments(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above products and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. A method of forming a multilayer structure, themethod comprising: forming a crystalline semiconductor nitride layer ona front surface of a silicon wafer handle substrate, wherein thecrystalline semiconductor nitride layer is selected from the groupconsisting of aluminum nitride, boron nitride, indium nitride, galliumnitride, aluminum gallium nitride, aluminum gallium indium nitride,aluminum gallium indium boron nitride, and combinations thereof andfurther wherein the crystalline semiconductor nitride layer is formed bymetalorganic chemical vapor deposition occurring by a reaction betweenan organic compound or a metalorganic compound and a nitrogen-containingprecursor and wherein the silicon wafer handle substrate comprises twomajor, generally parallel surfaces, one of which is the front surface ofthe silicon wafer handle substrate and the other of which is a backsurface of the silicon wafer handle substrate, a circumferential edgejoining the front and back surfaces of the silicon wafer handlesubstrate, and a bulk region between the front and back surfaces of thesilicon wafer handle substrate, wherein the silicon wafer handlesubstrate has a minimum bulk region resistivity of at least about 500ohm-cm; forming a silicon dioxide layer having a thickness between about500 nanometers and about 2 micrometers in interfacial contact with thecrystalline semiconductor nitride layer; and bonding a dielectric layerin interfacial contact with a front surface of a semiconductor donorsubstrate to the silicon dioxide layer in interfacial contact with thecrystalline semiconductor nitride layer to thereby form a bondedstructure, wherein the semiconductor donor substrate comprises twomajor, generally parallel surfaces, one of which is the front surface ofthe semiconductor donor substrate and the other of which is a backsurface of the semiconductor donor substrate, a circumferential edgejoining the front and back surfaces of the semiconductor donorsubstrate, and a central plane between the front and back surfaces ofthe semiconductor donor substrate.
 2. The method of claim 1 wherein thesilicon wafer handle substrate is sliced from a single crystal siliconingot grown by the Czochralski method or the float zone method.
 3. Themethod of claim 1 wherein the silicon wafer handle substrate has a bulkresistivity between about 500 Ohm-cm and about 100,000 Ohm-cm.
 4. Themethod of claim 1 wherein the silicon wafer handle substrate has a bulkresistivity between about 1000 Ohm-cm and about 100,000 Ohm-cm.
 5. Themethod of claim 1 wherein the silicon wafer handle substrate has a bulkresistivity between about 1000 Ohm-cm and about 10,000 Ohm-cm.
 6. Themethod of claim 1 wherein the silicon wafer handle substrate has a bulkresistivity between about 2000 Ohm-cm and about 10,000 Ohm-cm.
 7. Themethod of claim 1 wherein the silicon wafer handle substrate has a bulkresistivity between about 3000 Ohm-cm and about 10,000 Ohm-cm.
 8. Themethod of claim 1 wherein the silicon wafer handle substrate has a bulkresistivity between about 3000 Ohm-cm and about 5,000 Ohm-cm.
 9. Amethod of forming a multilayer structure, the method comprising: formingan amorphous semiconductor nitride layer on a front surface of a siliconwafer handle substrate, wherein the amorphous semiconductor nitride isselected from the group consisting of aluminum nitride, boron nitride,indium nitride, gallium nitride, aluminum gallium nitride, aluminumgallium indium nitride, aluminum gallium indium boron nitride, andcombinations thereof and further wherein the amorphous semiconductornitride layer is formed by metalorganic chemical vapor depositionoccurring by a reaction between an organic compound or a metalorganiccompound and a nitrogen-containing precursor and wherein the siliconwafer handle substrate comprises two major, generally parallel surfaces,one of which is the front surface of the silicon wafer handle substrateand the other of which is a back surface of the silicon wafer handlesubstrate, a circumferential edge joining the front and back surfaces ofthe silicon wafer handle substrate, and a bulk region between the frontand back surfaces of the silicon wafer handle substrate, wherein thesilicon wafer handle substrate has a minimum bulk region resistivity ofat least about 500 ohm-cm: forming a silicon dioxide layer having athickness between about 500 nanometers and about 2 micrometers ininterfacial contact with the amorphous semiconductor nitride layer; andbonding a dielectric layer in interfacial contact with a front surfaceof a semiconductor donor substrate to the silicon dioxide layer ininterfacial contact with the crystalline semiconductor nitride layer tothereby form a bonded structure, wherein the semiconductor donorsubstrate comprises two major, generally parallel surfaces, one of whichis the front surface of the semiconductor donor substrate and the otherof which is a back surface of the semiconductor donor substrate, acircumferential edge joining the front and back surfaces of thesemiconductor donor substrate, and a central plane between the front andback surfaces of the semiconductor donor substrate.
 10. The method ofclaim 1 wherein the crystalline semiconductor nitride layer comprisesaluminum nitride.
 11. The method of claim 1 wherein the crystallinesemiconductor nitride layer comprises boron nitride.
 12. The method ofclaim 1 wherein the crystalline semiconductor nitride layer comprisesindium nitride.
 13. The method of claim 1 wherein the crystallinesemiconductor nitride layer comprises gallium nitride.
 14. The method ofclaim 1 wherein the crystalline semiconductor nitride layer has anaverage thickness of between about 1 nanometer and about 2000nanometers.
 15. The method of claim 1 wherein the crystallinesemiconductor nitride layer has an average thickness of between about 5nanometers and about 1000 nanometers.
 16. The method of claim 1 whereinthe crystalline semiconductor nitride layer has an average thickness ofbetween about 5 nanometers and about 500 nanometers.
 17. The method ofclaim 1 wherein the crystalline semiconductor nitride layer has anaverage thickness of between about 5 nanometers and about 200nanometers.
 18. The method of claim 1 wherein the semiconductor donorsubstrate comprises a silicon wafer sliced from a single crystal siliconingot grown by the Czochralski method or the float zone method.
 19. Themethod of claim 1 wherein the semiconductor donor substrate comprises asilicon wafer sliced from a single crystal silicon ingot grown by theCzochralski method.
 20. The method of claim 1 wherein the dielectriclayer in interfacial contact with the semiconductor donor substrate isselected from the group consisting of silicon dioxide, silicon nitride,hafnium oxide, titanium oxide, zirconium oxide, lanthanum oxide, bariumoxide, and any combination thereof.
 21. The method of claim 1 furthercomprising heating the bonded structure at a temperature and for aduration sufficient to strengthen the bond between the dielectric layerin interfacial contact with the semiconductor donor structure andsilicon dioxide layer in interfacial contact with the crystallinesemiconductor nitride layer.
 22. The method of claim 1 wherein thesemiconductor donor substrate comprises an ion implanted damage layer.23. The method of claim 22 further comprising mechanically cleaving thebonded structure at the ion implanted damage layer of the semiconductordonor substrate to thereby prepare a cleaved structure comprising thesilicon wafer handle substrate, the crystalline semiconductor nitridelayer in contact with the front surface of the silicon wafer handlesubstrate, the silicon dioxide layer in interfacial contact with thecrystalline semiconductor nitride layer, the dielectric layer in contactwith the silicon dioxide layer, and a semiconductor device layer incontact with the dielectric layer.
 24. The method of claim 23 furthercomprising heating the cleaved structure at a temperature and for aduration sufficient to strengthen the bond between the dielectric layerand the silicon dioxide layer.